1. Taking school photos would be a good example of when to use main light fill & background because when capturing the photo you want to make sure that the lighting works well with the image and also the background light.
2.You would use side lighting on a model for a cosmetic magazine cover because when using the side lighting it brings out the part of the face thats facing the light. There are disadvantages to side light because when you capture the image the other half of the persons face will be dark .
3. You would use front light for for mainly capturing faces. Using front light allows you to get a clear focused shot without any shadows. Depending on the photographer , if the photographer wants to capture a image with shadow front light wouldn’t be effective.
4. A Photoshoot for youth would be a great time when using wide angle distortion in a portrait because in this angle you can play around and show the size of the body from top to bottom. The head will be bigger then the feet. There are disadvantages because you cant get the full size of the body .